For rare Golden Age collectible muscle cars, it doesn't get any more elusive than the one-offs 1967 Shelby GT500 Super Snake and 1968 Shelby EXP500 Green Hornet, both of which hit bids into the millions. There were also some under-100 units produced factory drag cars like the 1963 Chevy Impala Z11 and 1964 Mercury Comet A/FX that are hard to find. When it comes to regular production classic-era rarities, however, the Plymouth Hemi 'Cuda is a unicorn, bordering on being a holy grail car.Produced for only two years, between 1970-1971, Plymouth built just 781 Hemi 'Cudas produced, 666 wicked rides in the first year and 115 not-so-evil ones in the next. The Hemi 'Cuda is the gold, or perhaps In-Violet, standard for rare classic muscle cars, but there are actually quite a few less common street machines out there. With Hemi 'Cudas, especially drop-tops, selling in the millions, these less common rides aren't quite as valuable, but some of them are up there, and it's just a matter of time before their scarcity puts them in the muscle car collectible elite. 1969 Ford Torino Talladega Production: 754 Units Mecum In the late 1960s, it was straight-up warfare between the automakers to make a dominant NASCAR racer and in 1969, Dodge fielded the crazy-as-hell Hemi-powered Daytona, with a bonkers nose cone and wild rear wing that made it super-aerodynamic and virtually unbeatable. Ford answered with their own "aerocar" the Torino Talladega, that wasn't quite as insane but surprisingly effective. To qualify it for competition, Ford had to hit the homologation number of 500 units sold to the public, but actually produced only 754 cars total. Equipped with a killer 429 Cobra Jet V8, the '69 Talladega is one of the rarest Ford big-blocks and the most underrated, with a $124,000 Hagerty Concours condition value, that pales in comparison to the half-million-dollar Boss 429s. 1970 Buick GSX Production: 678 Units Mecum The Buick 455 Stage 1 V8 was a 360-horsepower, 510 lb-ft of tire-scorching torque marvel that made the 1970 GSX the baddest GM muscle car of the Golden Age, with a 13.34-second quarter-mile. The GSX was a special mostly-appearance package for the '70 GS 455, with killer graphics and cooler wheels. Buick didn't build the GSX for racing, but rather wanted an amazing-looking ride in their show rooms that would generate interest and foot traffic. Just 678 GSX cars were made, with 491 in Saturn Yellow and 187 in Apollo White. Things get even rarer with the engines, as only 400 were equipped with the higher-performance 455 Stage 1 package, that added 10 ponies but more than $50,000 in value. 1967 Chevrolet Camaro Z/28 Production: 602 Units Mecum The Z/28 became the Chevy Camaro's top performance trim, but in its 1967 debut, was kind of tame in terms of street performance. The reason is that it was developed to compete in the Sports Car Club of America's (SCCA) Trans-Am racing series, which had a limit of 5.0 liters on engines. Chevy stroked the 327 V8 to get a qualifying 302 cubic inches that put out an okay 290 hp, but this was a car built for endurance, not dragging. With only 602 Z/28s built in '67, it is, however, one of the most collectible classic Camaros with a top condition value of $150,000, versus the $117,000 worth of the 375-hp SS 396. 1970 Ford Mustang Boss 429 Production: 499 Units Mecum The 1969-1970 Boss 429 came about because Ford wanted to homologate their 375-hp 429 Cobra Jet V8 for competition in NASCAR and possibly NHRA. They could have put it in the Torino, which was their racing car at the time, but instead did the most insanely awesome thing by shoehorning it under the hood of a fastback Mustang. Only 859 of these killer 'Stangs were built in '69, and even fewer in '70 with a minimal production run of 499 units. The twist here is that the '70s are rarer, but the '69s are more collectible with a Concours condition value of $428,000, versus $414,000 for the sophomore year. They are the same basic car, but the '70s are a little more refined with cooler appearance trim, so it should be the one to chase. 1971 Plymouth GTX 440+6 Production: 135 Units Mecum Pairing the upscale Plymouth GTX with the 440 Six-Barrel budget big-block seems like an oxymoron, but it was actually a no-brainer. The restyled 1971 GTX came loaded with every option and feature Plymouth had to offer, meaning it was a little pricey, so optioning the cheaper 440 Six-Barrel over the expensive 426 Street Hemi made the price tag sting a little less. It was a way to get a 385-hp, 490 lb-ft of torque 13-second ride less expensively. Despite being an obvious ass-kicker, only 135 cars were optioned that year, so maybe it was a full-brainer, whatever the heck that is. In any case, this ultra-rare Mopar is comparatively affordable with a $164,000 top condition value, or about half of what a '71 GTX Hemi is worth. 1966 Dodge Charger Hemi Production: 118 Units Mecum A lot of people think that Hemi-equipped Dodge Chargers were plentiful in the classic-era, but it was actually a fairly rare pairing. In the case of the '66 Charger, it is extremely rare with only 118 of them leaving the factory with a 425-hp, 490 lb-ft of torque 426 Hemi V8. Another misconception is that the Golden Age Chargers were a raging success, but the first-gen almost qualifies as a flop. After moving a respectable 37,344 units in its 1966 debut, the 1967 Charger only sold 15,788 cars, making it one of the smallest batch Mopar muscle cars ever. While underappreciated back in the day, the rarity of the '66 Charger Hemi has made it a top draw for collectors, with a perfect condition value of $129,000. 1970 Dodge Challenger Six-Pack R/T - 116 Units Production: 116 Units Mecum When the Dodge Challenger hit the scene in 1970, it was an immediate sensation, selling 76,935 cars, but very few buyers exercised the 440 Six-Pack V8 option. There were 356 Hemi R/Ts in 1970, which is a rarity, but with only 116 440 Six-Packs, it's the unicorn car of this model year. The Six-Pack only added $320 to the $3,271 base price of a '70 Challenger R/T, while the Hemi option was a whopping $870. Performance-wise, the Hemi had an extra 35 ponies and was maybe a few tenths of a second quicker, but the Six-Pack was a solid 13.8-second car in the quarter-mile and could smoke anything GM or Ford had to offer, for less. In the current market, a '70 Challenger Six-Pack R/T is a steal with a $127,000 Concours condition value, when compared to the $245,000 that the Hemis go for. 1969 Dodge Hemi Daytona Production: 41 Units Mecum The 1969 Charger Daytona is the aerocar that Dodge built to dominate NASCAR, which it did a little too effectively, which eventually got it banned from competition. Before all of that, the car had to be homologated, meaning they had to sell at least 500 units to the public to qualify it as a stock car. Dodge allegedly sold 503 of these crazy-looking rides, but there are rumors that they used VINs from normal Chargers, and the real number of Daytonas could be far less. The Hemi-equipped Daytona total is also in dispute, with many sources citing 70 cars, but some sources indicate as few as 41 units. This is a super-rare, hyper-collectible Mopar that has sold for as much as $3.3 million at a Mecum auction while its flawless condition value is ridiculously underpriced at $874,000. 1971 Dodge Hemi Super Bee Production: 22 Units Mecum The bare-bones Super Bee, introduced mid-model year in 1968, set the standard for affordable Dodge badassery as a stripped-down speed machine. Sadly, it was discontinued in 1970, but lived on as a trim in 1971 for the third-gen Charger. Like its predecessor, the '71 Charger Super Bee was a no-frills, high-performance ride, but it could be optioned with plenty of frills, including the 426 Street Hemi V8. Only 22 people took the Super Bee to its Hemi extreme in '71, and apparently most of those cars have been lost to time, as it's almost a Holy Grail now, with next to no presence on the collector's scene. The once-budget Mopar has a tip-top condition value of $281,000, but because of its elusiveness, there could be a low-mileage survivor car out there that could potentially hit the million-dollar mark. 1970 Dodge Coronet Hemi R/T Production: 14 Units Mecum The Dodge Coronet had always been a solid working-class muscle car, but its boxy design and complete lack of style didn't excite people the way the second-gen Charger or first-gen Challenger did. In 1970, however, the Coronet got some hot Coke bottle curves and the most wicked front fascia of the entire Golden Age, giving it an ominous presence that ranks as one of the most wicked classic-era Mopars. The '70 Coronet R/T also added killer twin hood scoops, making it even more badass, which only added to its aggressive persona. This gorgeous beast with a 426 Street Hemi should have been the muscle of the year, but only 14 were ordered, resulting in one of Mopar's rarest rides. The '70 Coronet Hemi R/T was slept-on in its time, and people are still kind of drowsy on it today with an undervalued $146,000 Concours condition value.Sources: Hagerty, Mecum